Portable panels wire size

[AStinker-]

Hey guys, I need some help. Would you consider giving me some advice please?

I’m putting together a portable solar panel setup. The panel’s will be the following.

Max Power: 140Wp
Open Circuit Voltage (Voc): 21.0V
Short Circuit Current (Isc): 8.40A
Maximum Power Voltage (Vmp): 17.0V
Maximum Power Current (Imp): 8.00A

Originally I was planning on paralleling 2 of them on the same wires and just jumpering directly to my batteries when I need to use them but several said don’t do it that way so I got scared and decided I will probably get a controller. It will probably be PWM Charge Controller big enough so I can use it when I do a permanent roof install.

I would like to be able to set the panels up at least 100 ft from my batteries / (PWM Controller) if necessary to find sunlight. I was planning on using a 2 conductor 10 ga stranded wire to accomplish this. But after reading all the discussion on wire size from solar panels to controller on the thread mena661 started “Panel to Solar Controller Wire Size” for his new solar build I’m wondering if I will have too much of a voltage drop at that distance. So I would appreciate your advice if you would consider it. Will 100 ft of 10 ga wire from 2 of these panels work or not?

It would not be a deal breaker if I need to add a 2nd cable or even a 3rd if I needed to as I can buy 100 ft of stranded 2 conductor 10 ga wire for $35.00. The problem is I don’t know what I need.

I’m not sure I’m using the calculator that was posted on mena661’s thread correctly but what I am entering is Wire Size: 10 AWG Voltage: 21.8 Phase: DC Number of conductors: Single set of conductors Distance: 100 Ft Load Current : 8.95 Amp. The RESULTS: Voltage drop: 1.79 Voltage drop percentage: 8.21% Voltage at the end: 20.01. Will it work but not efficiently??? I don’t know. Then when I increase Load Current for 2 panels to 17.9 Amps it doubles the losses which drops the Voltage at the end to 18.22 volts. But also I don’t know what the minimum voltage into the controller should be for it to achieve reasonable bulk & absorption charge when batteries are at 50 to 80% SOC.

My short term reason for solar is to supplement my generator when off grid where there is limited generator run time. I want to get the most out of the panels that I can with existing conditions but right now I do not need the panels for topping off or equalizing my batteries. I will have a 485 Amp battery bank, will be off grid no more than 4 days at a time & will be on back on grid afterwards long enough to top off & equalize batteries as necessary. My problem is I will be running a 5 cu ft residential freezer with an inverter. It pulls 1.4 amp AC & I anticipate it will run at a min 50% to a max 75% of the time. If 50% of the time it will take 180 of my 240 usable amps if 75% of the time it will use over my 240 usable amps. I have a 55 amp Iota converter with Q4 controller plus a portable 40 amp charger I will be running with a generator but concerned if I can only get 2 or 3 hours of gen run time. My goal is to get as much as possible but hopefully at least supplement enough amp hrs from the portable to keep from killing my batteries. I think I will need to have the controller set so it never has over a 14.9 or 15 volt temperature compensated output but I don’t know what the voltage from the solar panels need to be to accomplish this when my batteries are at say a 60% SOC. If you could advice me it would be greatly appreciated.

Thanks,
Alan

[BFL13]

JiminDenver wrote:
Would it be possible to mount a inverter under the hood of the truck and use it while under way to run the trailers converter?

I couldn't do it parked with the hood open. I had to hang the inverter out over the fender so it was not getting so hot that it would shut down.

Maybe if the inverter were under the engine instead of higher up by the battery? Needs to be out of the heat.

You have the first limit- the inverter has to have the watts to run the converter at whatever amps. Second limit- the truck's own voltage has to stay up at 13.8ish while the inverter is drawing on the battery.

With mine, I could run a 35amp Vector at 35a (needs 600w input) with a 1000w inverter. If you put too much on the inverter, the truck voltage needle drops down to the left from being upright so that tells you when you went over the limit.

[pianotuna]

Hi Jim,

In theory yes, but, under the hood is hot and there may be a lot of vibration as well. Mount in the cab might be better.

JiminDenver wrote:
Would it be possible to mount a inverter under the hood of the truck and use it while under way to run the trailers converter?

[JiminDenver]

Would it be possible to mount a inverter under the hood of the truck and use it while under way to run the trailers converter?

[AStinker-]

pianotuna wrote:
Hi,

Reconsider a fixed install--then solar will charge as you travel. It's kind of neat in my class c to observe the solar panels sending energy back to the chassis.

I have a generator on a rack and on a previous RV would use it to power the roof air while trundling down the road. That could have been a nice big fat converter instead.

I do have the same system available for use on my current Rv but haven't used it much--and never specifically for battery charging.

All that is needed is a safe way to connect the shore power cord to the generator.

Not to worry tuna a fixed install is in my future plans and remember we are still newbees at this RV'ing thing. We have to make sure we can do this without killing one another. And if I don't learn to pay better attention to that GPS gizmo that makes me miss all those turns the DW may decide RVing isn't in our future. 🙂

[AStinker-]

Almot wrote:
You won't have inverter/freezer running all the time. Those freezers that I know, are cycling. So there is no guarantee that there won't be some periods when the battery has no loads and the cold weather mandates Absorption ~15V. To be on the safe side, I would try keeping the voltage drop so as to provide the controller input not lower than 15 at 77F. It can be higher than 15, - the controller will limit the upside as you said - but it shouldn't be lower than 15.

AC freezer does render the whole debate kind of moot. With a load like this, plus your other loads, a 140W panel is very, very little, in terms of daily amp-hours. You will still have to run a genny some hours every day. And, with almost permanent high current of the freezer - off cycles won't be long enough - you won't benefit from finishing the charging silently with a low current of the panel.

Thanks Almot... that 15v will be my goal. I will get it there one way or another. I will have "2" 140W panels btw and no they won't come close to meeting my needs but if I get everything right they should be a nice supplement to my needs. I'm not sure the Freezer will be a permanent fixture either, but something we wanted to have for our trip this summer. If it turns out to be a big PITA it will come out, time will tell.

[pianotuna]

Hi,

Reconsider a fixed install--then solar will charge as you travel. It's kind of neat in my class c to observe the solar panels sending energy back to the chassis.

I have a generator on a rack and on a previous RV would use it to power the roof air while trundling down the road. That could have been a nice big fat converter instead.

I do have the same system available for use on my current Rv but haven't used it much--and never specifically for battery charging.

All that is needed is a safe way to connect the shore power cord to the generator.

[Almot]

You won't have inverter/freezer running all the time. Those freezers that I know, are cycling. So there is no guarantee that there won't be some periods when the battery has no loads and the cold weather mandates Absorption ~15V. To be on the safe side, I would try keeping the voltage drop so as to provide the controller input not lower than 15 at 77F. It can be higher than 15, - the controller will limit the upside as you said - but it shouldn't be lower than 15.

AC freezer does render the whole debate kind of moot. With a load like this, plus your other loads, a 140W panel is very, very little, in terms of daily amp-hours. You will still have to run a genny some hours every day. And, with almost permanent high current of the freezer - off cycles won't be long enough - you won't benefit from finishing the charging silently with a low current of the panel.

[BFL13]

Yes we use provincial parks but before school gets out end June or after Labour Day. Can't get near those places in the summer when school is out. They do have a reservation system but you have to book really early. Wouldn't work for us, where we like to be wandering along without a tight schedule.

Suggest the Can/Alaska forum for tips on all that side of things.

Honda is behind the cab. I have tried charging loose batteries in the truck bed from a portable charger on the Honda. Works. Not tried it with an extension cord back to the trailer with the charger back there on the installed batteries (or instead to the shore power cord to run the converter) but see no big deal there if you can keep the cords off the ground.

[AStinker-]

BFL13 wrote:

AStinker- wrote:
Thanks tuna will keep that in mind. No not full time. If all goes as planned we will be leaving form home the middle of May heading to Alaska for the summer. Will be living in it till the middle to end of October. Will see how that goes The DW thinks she want to go full time but I want to check out the water a bit more first.

Being on the road Rving and stopping at off-grid parks (as with most BC provincial parks, which are in the woods -no good for solar) brings its own challenges for keeping the batts up.

You don't have time in the morning before heading out to do any generator recharging. (BC parks have gen hours 9-11am and 6-8pm) so you need to get there early enough to do the 6-8pm or else go to a private park with full hook ups. Also back to the big charger to get it done in two hours!

In fact we have to go to where there is shore power every so often on the road or the batts will die---there is no hope for the 7-pin charging pitiful amount or any real solar while on the road.

If your solar is on the roof you could get a bit done while driving before you go into the woods for the night. I have a portable panel I leave on the roof in its wooden tray strapped down with bungee cords while travelling but can set it up on the ground too.. max flex!

If pressed, I would figure out a way to run the trailer's converter from the Honda that is in the truck bed for going down the road instead of relying on the stupid 7-pin. Would need a 120v, 15a line alongside the 7-pin line back to the trailer.

One issue with that is when I have tried to run the Honda in the truck bed going down the road, every so often it quits. Something to do with the air supply in the vortex back there I think. Just have to keep an ear open to hear if it is still running and pull over to restart it as required.

Yes I will be set up to run the gen & converter while driving. Is your gen up next to the cab or back by the tailgate? I need to experiment & see if my gen will run while driver I guess. With the 5th wheel there is some strange air movement back by the tail gate. I've had empty coolers sucked up against the overhang and would have gone out if space had been bigger. Do you know of a foolproof safe way of connecting a portable charger to batteries and running it with gen while traveling?

When traveling do you mainly us provincial parks?

[BFL13]

AStinker- wrote:
Thanks tuna will keep that in mind. No not full time. If all goes as planned we will be leaving form home the middle of May heading to Alaska for the summer. Will be living in it till the middle to end of October. Will see how that goes The DW thinks she want to go full time but I want to check out the water a bit more first.

Being on the road Rving and stopping at off-grid parks (as with most BC provincial parks, which are in the woods -no good for solar) brings its own challenges for keeping the batts up.

You don't have time in the morning before heading out to do any generator recharging. (BC parks have gen hours 9-11am and 6-8pm) so you need to get there early enough to do the 6-8pm or else go to a private park with full hook ups. Also back to the big charger to get it done in two hours!

In fact we have to go to where there is shore power every so often on the road or the batts will die---there is no hope for the 7-pin charging pitiful amount or any real solar while on the road.

If your solar is on the roof you could get a bit done while driving before you go into the woods for the night. I have a portable panel I leave on the roof in its wooden tray strapped down with bungee cords while travelling but can set it up on the ground too.. max flex!

If pressed, I would figure out a way to run the trailer's converter from the Honda that is in the truck bed for going down the road instead of relying on the stupid 7-pin. Would need a 120v, 15a line alongside the 7-pin line back to the trailer.

One issue with that is when I have tried to run the Honda in the truck bed going down the road, every so often it quits. Something to do with the air supply in the vortex back there I think. Just have to keep an ear open to hear if it is still running and pull over to restart it as required.

[AStinker-]

Thanks tuna will keep that in mind. No not full time. If all goes as planned we will be leaving form home the middle of May heading to Alaska for the summer. Will be living in it till the middle to end of October. Will see how that goes The DW thinks she want to go full time but I want to check out the water a bit more first.

[pianotuna]

Hi,

It will take between 25 and 50 cycles for the batteries to reach their full capacity with most of the improvement coming from the first 15 cycles.

So it may be important to NOT do 50 to 90 for the first few cycles.\

Are you full time in the rv?

[AStinker-]

BFL13 has it exactly right. He said… “In the OP's case, he has that freezer inverter load going all day, so his battery voltage is never going to get very high.” Exactly and is why I was originally going to connect directly to the battery without a controller. But after what if’ing it I decided why take the risk and decided to add a controller now since I expect to need one latter anyway.

He said… “He will do better with the solar than without it, but he is still going to be a generator and charger guy.” Again exactly right. And if I’m going to spend my money on some solar I not only want to maximize my return but more importantly I think I’m going to need all the amps I can scrounge up.

Then BFL13 said… “Sooo, as the OP has been saying, he has two things to do:
A. get some solar- simple portable (say two 120w for ease of handling instead of one heavy huge 240) on cheap PWM on a long wire for parking in the shade. Don't fuss about exactly how much it will do, just accept whatever it does for you any given day…. Exactly right again except that is not my nature “not to fuss.” And right or wrong all of the above is on order with only some minor differences. And as for cables I’m going to do like Tom M is doing and make up different length cables because I’m guessing there will be locations that 25 or 50 feet may be all I need to find sun. And right or wrong I’m going to get another roll of the cheap 2 wire #10 AWG wire like I already have and either make up a set of cables for each panel (hey I may be too lazy to set up both panels sometimes) or combine them into one if after some more garbage in garbage out stuff with those wire loss calculators tell me to.

B. get the biggest amp charger his generator can run (PowerMax 75,85, and 100 amper size are PF corrected so a Honda 2000 ought to be able to run one--I don't know for sure) This will probably be my next school of hard knocks. I’m going to try and get by with my 55 amp Iota and a portable. I have, right or wrong a 2K Champion and access to a 2nd one if I need it. I don’t know yet what it is capable of or what its limitations are but will start playing with it after I get my batteries all in.

Speaking of batteries, I think I read in a thread some time back but can’t find it now, that you should break in new batteries and suggestions on how to do it. If that is correct and any one can point me to it I would be forever grateful. And if anyone wants to make suggestions I will graciously accept them. I have 2 new T-105’s. I have charged them, run a recondition cycle, run an equalize cycle with a VEC1098 & put them on a battery minder since I brought them home. Do I need to do anything else before I start using them hard?

I have learned so much from all you guys it is unbelievable. Just know that each and every one of you are appreciated, even the guys that have not said anything because odds are I have read & learned something you have contributed in different thread.

Thanks everyone and

GO WSU!!!! :B

[BFL13]

Your 15v limit will not be reached anyway IMO, so don't worry about it. Also that 15 is at the battery not at the controller.

On solar in the afternoon with battery voltage finally above 14v, your amps are going to taper as battery nears full. But the voltage will only keep climbing if there is no equal or greater draw on the batteries at the same time. It doesn't take much of a draw to equal what the solar is putting in by the time you are over 14v.

EDIT, I should make that draw to be higher than the solar amps. Until they are equal, the battery will still charge and the solar will run the draw as well, so the draw has to be higher than the total solar before the batts don't get anything and voltage stops rising.

That is why I figure the highest SOC I will ever get to on any day is sometime before supper when I start using battery after not using it much in the afternoon. (Which allows the battery voltage to climb in the afternoon)

Once I start using things like the inverter, that knocks battery voltage right down. The only restriction is that the pre-supper/late afternoon voltage not be over 15 or the inverter won't work to help make supper.

In the OP's case, he has that freezer inverter load going all day, so his battery voltage is never going to get very high. He will do better with the solar than without it, but he is still going to be a generator and charger guy. The idea then is to have "some solar" to reduce the time the generator has to run each day, plus have a high amp charger for the generator to use.

Four hours on four batts is a very long time for a 50-90 recharge.

I can do a 50-90 on six batts in two and a half hours and I can do a 50-90 on four of them in two hours. However that is using 140 amps on the six and 105 on the four. ( PowerMax 100 amper and VEC1093 40amper)

Now the limit is how many charger amps can the generator support --eg my Honda 3000 can do 130amps of non-PF corrected chargers. 131amps will make it conk out. The 100amper is PF corrected so I can actually go to 150a with the 100 plus another 50 of non-PF.

Sooo, as the OP has been saying, he has two things to do:

A. get some solar- simple portable (say two 120w for ease of handling instead of one heavy huge 240) on cheap PWM on a long wire for parking in the shade. Don't fuss about exactly how much it will do, just accept whatever it does for you any given day.

B. get the biggest amp charger his generator can run (PowerMax 75,85, and 100 amper size are PF corrected so a Honda 2000 ought to be able to run one--I don't know for sure)